Hi, I am trying to install an aftermarket cd player for my girlfriend's brother. He has a 94 Ford F-150, and I got the harness for it to connect it directly to the factory wiring. Well, I plugged it in and the power came on and everything appeared to be ok, but there was no sound. I plugged the factory head unit back in and everything was fine. I then checked the cd player and it still works and I can get sound out of it when just connected to a speaker and battery. I am assuming that there must be some sort of factory amp. If this is the case, what are my options. I guess, where is it so I can bypass it. Thanks for any help.